Patent GB-737480-A (GB)
Title: Equipment for the simultaneous supervision of current consuming devices some of which are continuously and some of which are only intermittently in operation
IPC: B60Q11/00
Filed: 1952-12-01
Abstract: 737,480. Lamp failure alarms ; road-traffic signals on vehicles. PARTL, W. Dec. 1, 1952 [Nov. 30, 1951], No. 30385/52. Class 118 (2). Apparatus for simultaneous supervision of current consuming devices, some of which are continuously in operation and some in action for short periods only comprises a first relay U having opposed windings, one of which is in series with a continuously operating device and the other of which is supplied with current so that the magnetic fields cancel out, a second relay having windings in series with the intermittently operable devices and a winding in series with a contact closed when the magnetic balance of the first relay is disturbed and also in series with a contact opened when the second relay is energized, and a warning lamp lit by contacts closed when the second relay is energized. A first relay U has a winding W1 in series with vehicle tail lamps TL and an opposed winding W2 in series with a resistor R such that the magnetic effect of the normal current to the tail lamps is balanced out. Both windings are fed by the switch S1. The armature of relay U controls three sets of contacts. Á1, Á2 and u3, which are normally open. A second relay K has three windings W3, W4 and W5 and its armature controls three sets of contacts k1, k2 and k3. When energized relay K opens contacts k2 and closes contacts kl and k3. The winding W3 is in series with contacts u3 of relay U. The winding W4 is in series with direction indicators D1 and D2, selectively operated as required by switch S3. Winding W5 is in series with winding W4 and stop lamp SL with brake-operated switch S2. If a tail lamp fails the magnetic balance of relay U is upset and all three of its contacts close. Contacts u1 and u2 short-circuit the windings and hence the relay chatters. Contacts u3 energize winding W3 of relay K, causing contacts k2 to be opened. Therefore relay K also chatters and contacts k1 and k3 cause the warning lamp WL to flicker. If the stop lamp SL is lit, windings W4 and W5 are energized and contact k3 shorts winding. W4; but winding W5 is sufficient to hold relay K operated and hence lamp WL is lit steadily over contacts k1 and k3. Operation of either direction indicator D1 or D2 energizes winding W4 which is thus shorted by contacts k3 and relay K chatters and lamp WL flickers to remind the driver that S3 is operated. If, however, the stop lamp SL is lit whilst a direction indicator is in operation, the chattering will cease and lamp WL glow steadily since winding W5 is sufficient to hold relay K operated. Thus, annoyance due to continual chattering of the relay while waiting to turn at a road junction is automatically avoided by the fact that the brake is applied, the chattering being resumed when the brake is released and until switch S3 is restored. It is preferred to provide means for adjustment of the armature position or spring tension from outside of the device so that the response sensitivity can be varied to compensate for small variations in current taken by lamps even when of the same nominal wattage rating.